Our long-term aim is to develop and evaluate effective treatment programs for alcohol-related problems among trauma patients. However, before such programs can be developed, it is essential to clearly identify the different groups of problem drinkers in order to effectively target treatment programs. Central to this is the ability to clearly distinguish those with alcohol dependency from those with an abuse problem. The unique contribution of this study will be its ability to clearly identify important subgroups of problem drinkers to which very different treatment efforts will need to be targeted. The other unique contribution of this study is its ability to examine the prevalence of other substance abuse and its coexistence with alcohol-related problems. The prevalence of alcohol abuse/dependence will be assessed among 1 ,350 patients admitted to a Level I trauma center over two years. The subjects will be trauma patients who are 18 years of age or older, with normal cognitive functioning (Glasgow Coma Scale score of 15). The diagnosis of alcohol problems will be based on 1) admitting blood alcohol determinations and toxicology screening tests for other drugs of abuse (including marijuana), 2) biologic markers, including serum gamma-glutamyltransferase and asparatate aminotransferase levels, mean corpuscular volume, and other tests related to liver function and other markers that may reveal pathophysiologic changes related to acute or chronic alcohol abuse (platelet counts, serum amylase, glucose, etc.), 3) interview administered CAGE and Brief-MAST screening tests and the in-depth Psychoactive Substance Use Disorders section of the Structured Clinical Interview for DSM-III-R (SCID), and 4) history of trauma and alcohol use as measured by AUDIT. The entire PSUD/SCID assessment will be used to make the diagnosis of alcohol abuse/dependence. The sensitivity and specificity of individual biologic data and screening interview results to diagnose alcohol abuse/dependence will be examined. In addition, biologic and interview data (including individual question$ from the interview instruments) will be analyzed to ascertain methods of identifying patients with alcohol abuse/dependence problems. Also, patient driving records will be examined to determine if information obtained from them may be used to help profile the alcoholic trauma patient.